1. Field of the Invention
The present invention relates generally to prosthetic feet utilized to allow below-knee amputees to walk, and particularly to a prosthetic foot that is capable of generating a suitable thrust for propelling the deficient limb of an amputee forward in walking.
2. Description of the Prior Art
A below-knee amputee cannot be provided with a thrust that can be obtained by pushing the ground with his toes, owing to the loss of plantar flexors. It is reported that he consumes 20% more oxygen than an able-bodied person, when the below-knee amputee walks at a speed of 50 to 90 m/min. This means that the below-knee amputee consumes more energy than an able-bodied person in walking, so that he gets easily exhausted.
In order to reduce the above-mentioned below-knee amputees"" difficulty, there has been developed improved prosthetic feet that allow the below-knee amputees to walk naturally and with low energy consumption.
FIG. 1 is a schematic diagram showing a conventional energy storage type prosthetic foot.
The conventional prosthetic foot shown in FIG. 1 is disclosed by Korean Pat. No. 0155591 entitled xe2x80x9cenergy storage type prosthetic foot pylonxe2x80x9d.
Referring to the drawings of the Patent, the conventional prosthetic foot pylon comprises a first pylon member 18, a second pylon member 20, one or more plate springs 22 combined with the first and second pylon members 18 and 20 for controlling the axial and rotational movements of the first and second pylon members 18 and 20, and a foot member 14 fixed to the second pylon member 20.
The conventional prosthetic foot pylon is characterized in that each plate spring 22 is combined with the first and second pylon members 18 and 20. Consequently, forces applied to the pylon members 18 and 20 are stored in the plate spring 22 as elastic energy, and upon the removal of the forces, the energy stored in the plate spring 22 is released to generate a thrust.
U.S. Pat. Nos. 5,181,932, 5,486,209 and 5,593,457 entitled xe2x80x9cfoot prosthetic having auxiliary ankle constructionxe2x80x9d and U.S. Pat. No. 5,037,444 entitled xe2x80x9cprosthetic footxe2x80x9d disclose typical prosthetic feet and employ keels having plate spring structures.
U.S. Pat. No. 5,158,570 entitled xe2x80x9cfoot prosthesis having auxiliary ankle constructionxe2x80x9d and U.S. Pat. No. 5,258,038 entitled xe2x80x9cprosthetic foot with ankle joint and toe memberxe2x80x9d disclose prosthetic feet in each of which a forefoot member, an ankle member and a heel member formed of thermoplastic material or composite material are connected to one another through joints. These are multi-piece prosthetic feet in which pivotable movement is performed while being resisted by elastomeric pads.
U.S. Pat. No. 5,219,365 entitled xe2x80x9cprosthetic footxe2x80x9d discloses a prosthetic foot in which a forefoot member, an ankle member and a heel member are fabricated to be a single integrated keel and are formed of hardened acetal copolymers. A vertical through hole is formed in the keel and serves to connect the keel with leg assemblies. The arched configuration of the prosthetic foot increases the strength and dynamic characteristics of the foot.
U.S. Pat. No. 5,443,527 entitled xe2x80x9cprosthetic foot and three-way ankle jointxe2x80x9d and U.S. Pat. No. 5,695,526 entitled xe2x80x9cone-piece mechanically differentiated prosthetic foot and associated ankle joint with syme modificationxe2x80x9d disclose prosthetic feet each of which includes an integrated instep and sole portion and is provided with joints to provide for three-axis rotation, dorsiflexion and planarflexion.
U.S. Pat. No. 5,443,528 entitled xe2x80x9ccoil spring prosthetic footxe2x80x9d, U.S. Pat. No. 5,695,527 entitled xe2x80x9ccoil prosthetic footxe2x80x9d, U.S. Pat. No. 5,653,767 entitled xe2x80x9cprosthetic footxe2x80x9d and U.S. Pat. No. 5,571,213 entitled xe2x80x9cprosthetic footxe2x80x9d disclose prosthetic feet that are fabricated of continuous springs. Each prosthetic foot comprises a foot center coil section, a heel extension section and a forefoot extension section that are formed of epoxy-like polymer associated with graphite fiber, a mixture of graphite fiber and glass fiber, Kevlar, spectra or one of other fiber materials. The prosthetic foot allows lateral medial torsional movement. The heel extension section integrated with the forefoot extension section is utilized, so that the prosthetic foot is designed to transmit energy from a heel to a forefoot effectively.
U.S. Pat. No. 5,258,039 entitled xe2x80x9cenergy storing composite prosthetic footxe2x80x9d discloses a keel that is xcex-shaped, "khgr"-shaped and "sgr"-shaped. The keel is formed of resin impregnated carbon woven fabric composite material.
U.S. Pat. No. 5,509,937 entitled xe2x80x9cprosthetic foot with enhanced heel controlxe2x80x9d and U.S. Pat. No. 5,116,385 entitled xe2x80x9cmedio-lateral control enhancing, cantilever-spring type prosthetic footxe2x80x9d disclose prosthetic feet each of which comprises a main forefoot leg, a rear leg and an intermediate leg connecting the forefoot leg with the rear leg and is S-shaped. In the prosthetic feet, cantilever spring members absorb energy from the heel portions when the heels are brought into contact with the ground. The prosthetic feet provide medio-lateral control and release energy during a toe-off stage.
As described above, a variety of prosthetic feet have been developed throughout the world. These prosthetic feet employ various-shaped keels, respectively.
However, some of the prosthetic feet include both leg portions and foot portions, so that pylons cannot be attached to the prosthetic feet and the prosthetic feet have complicated structures due to a large number of parts.
Additionally, the prosthetic feet have narrow allowable ranges of variation that cannot allow the prosthetic feet to be designed to correspond to individual amputee""s physical conditions.
Accordingly, it is desired to develop a prosthetic foot that has adjustable design factors for amputee""s individual physical conditions and is capable of being easily fabricated.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a prosthetic foot, which allows a below-knee amputee to walk naturally, which reduces energy consumption in walking, and which is easily worn due to its simple structure.
In order to accomplish the above object, the present invention provides a prosthetic foot to be connected to a pylon that is utilized for the substitution of the shinbone of an amputee, comprising: an ankle portion to be secured to the pylon; a plurality of curved portions extended from one end of the ankle portion; and a sole portion extended from one end of the curved portions; wherein the ankle portion, the curved portions and the sole portion form a single integrated plate spring structure.
In accordance with one feature of the present invention, the curved portions are a first curved portion and a second curved portion, the first curved portion having a first predetermined radius of curvature and being extended from the inner end of the ankle portion, the second curved portion having a second predetermined radius of curvature and connecting the first curved portion with the sole portion.
In accordance with one feature of the present invention, the foot further comprises a planar portion, the planar portion having a first predetermined length and being interposed between the first and second curved portions.
In accordance with one feature of the present invention, the sole portion has a second predetermined length and is inclined at a predetermined slope.
In accordance with one feature of the present invention, the foot further comprises a toe portion, the toe portion having a third predetermined radius of curvature and being extended from the outer end of the sole portion.
In accordance with one feature of the present invention, the foot further comprises first, second and third connecting portions, the first connecting portion connecting the first curved portion with the planar portion, the second connecting portion connecting the heel portion with the sole portion, the third connecting portion connecting the sole portion with the toe portion, the first, second and third connecting portions respectively having predetermined fillet radii so as to reduce the concentration of stresses.
In accordance with one feature of the present invention, the foot further comprises an aluminum pad, the aluminum pad being fixed to a portion of the ankle portion that is brought into contact with the pylon.
In accordance with one feature of the present invention, the foot further comprises an elastic polymer pad, the elastic polymer pad being interposed between the ankle portion and the aluminum pad so as to increase the compliance of the ankle portion.
In accordance with one feature of the present invention, the ankle portion, the aluminum pad and the elastic polymer pad are provided with one or more through-holes so as to receive a bolt.
In accordance with one feature of the present invention, the ankle portion, the curved portions and the sole portion are made of fiber reinforced composite material.
In accordance with one feature of the present invention, the fiber reinforced composite material is formed by associating epoxy-like polymer with one of various chopped or continuous fibers, such as carbon fiber, Kevlar, graphite fiber and glass fiber.
In accordance with one feature of the present invention, the fiber reinforced composite material is formed of unidirectional prepreg or woven fabric prepreg.